阅读说明：本技术 盐间地层压力预测方法、装置、电子设备及介质 (Method and device for predicting pressure of stratum between salts, electronic equipment and medium ) 是由 钱恪然 姜大建 刘韬 刘来祥 刘喜武 刘炯 于 2020-05-18 设计创作，主要内容包括：公开了一种盐间地层压力预测方法、装置、电子设备及介质。该方法可以包括：构建盐间地层的岩石物理模型；根据岩石物理模型,计算盐间地层的弹性张量；根据弹性张量,计算每一个深度的正常压实纵波速度；根据每一个深度的正常压实纵波速度,构建正常压实趋势线,计算目标深度的地层压力。本发明通过构建盐间岩石物理模型,获取常压条件的弹性信息,提高了压实趋势线的精度,并结合Eaton地层压力预测方法,能够有效提高地层压力预测精度。(A method, an apparatus, an electronic device and a medium for predicting the pressure of a formation between salts are disclosed. The method can comprise the following steps: constructing a rock physical model of the salt stratum; calculating the elasticity tensor of the stratum between the salts according to the rock physical model; calculating the normal compaction longitudinal wave speed of each depth according to the elasticity tensor; and constructing a normal compaction trend line according to the normal compaction longitudinal wave speed of each depth, and calculating the formation pressure of the target depth. According to the method, the elasticity information under normal pressure conditions is obtained by constructing the rock physical model between the salts, the precision of the compaction trend line is improved, and the stratum pressure prediction precision can be effectively improved by combining an Eaton stratum pressure prediction method.)

1. A method for predicting pressure in an intersalt formation, comprising:

constructing a rock physical model of the salt stratum;

calculating the elasticity tensor of the stratum between the salts according to the rock physical model;

calculating the normal compaction longitudinal wave speed of each depth according to the elasticity tensor;

and constructing a normal compaction trend line according to the normal compaction longitudinal wave speed of each depth, and calculating the formation pressure of the target depth.

2. The method of predicting salt formation pressure of claim 1, wherein constructing the petrophysical model of the salt formation comprises:

according to the VRH average theory, uniformly mixing salt rock, glauberite and quartz minerals to obtain a mixture between salts;

according to the DEM theory, adding kerogen into the salt mixture to obtain an organic-rich salt mixture;

calculating the wet porosity and further calculating the wet clay skeleton;

according to the DEM theory, adding the wet clay skeleton into the organic-rich salt rock mixture to obtain a wet mineral skeleton;

according to the Gassmann theory, dry pores are added into the wet mineral skeleton to obtain a rock physical model.

3. The method of predicting salt formation pressure according to claim 2, wherein the wet porosity is calculated by formula (1):

wherein the content of the first and second substances,is the wet porosity of the clay, f_cIn order to consider the volume percentage of the clay in the pores,f_c ^min order to take the volume percentage of the mineral occupied by the clay regardless of the porosity,is the total porosity.

4. The method of predicting salt formation pressure according to claim 3, wherein the wet clay skeleton is calculated by equation (2):

wherein M is_wetIs the elasticity tensor of the wet clay skeleton, M_clayIs the elasticity tensor of clay.

5. The method of predicting salt formation pressure according to claim 2, wherein the petrophysical model is calculated by equation (3):

wherein the content of the first and second substances,for the elasticity parameter of the pore fluid, refer to Table 1, M_mix2Is the elastic tensor of the petrophysical model, M_mix1Is the elasticity tensor of the wet mineral skeleton.

6. The method of predicting salt formation pressure according to claim 1, wherein the normal compaction compressional velocity is calculated by equation (4):

wherein v is_{p_depth}For normal compaction longitudinal wave velocity, K and μ are the elastic tensors, and ρ is the total density for the corresponding depth.

7. The method of predicting salt formation pressure as claimed in claim 1, wherein the formation pressure at the target depth is calculated by equation (5):

wherein, P_pPressure value to be determined, P, for a target depth_ovTo overburden pressure value, P_wAnd v is the measured speed value of the target depth.

8. An apparatus for predicting a pressure of an intersalt formation, comprising:

the construction module is used for constructing a rock physical model of the salt stratum;

the elastic tensor calculation module is used for calculating the elastic tensor of the stratum between the salts according to the rock physical model;

the longitudinal wave velocity calculation module is used for calculating the normal compaction longitudinal wave velocity of each depth according to the elasticity tensor;

and the formation pressure calculation module is used for constructing a normal compaction trend line according to the normal compaction longitudinal wave speed of each depth and calculating the formation pressure of the target depth.

9. An electronic device, characterized in that the electronic device comprises:

a memory storing executable instructions;

a processor executing the executable instructions in the memory to implement the method of predicting salt formation pressure of any of claims 1-7.

10. A computer-readable storage medium, characterized in that the computer-readable storage medium stores a computer program which, when executed by a processor, implements the method of predicting the pressure in an intersalt formation according to any one of claims 1 to 7.

Technical Field

The invention relates to the technical field of oil and gas geophysical, in particular to a method and a device for predicting formation pressure between salts, electronic equipment and a medium.

Background

Formation pressure, also known as pore pressure, is an important engineered sweet spot parameter. In recent years, with the gradual deepening of domestic exploration and research on shale oil and gas reservoirs, people have deeper understanding on the exploitation of domestic marine shale gas resources. Particularly with the progressive commercial exploitation of Fuling shale gas reservoirs, it has been found that production from shale gas reservoirs is generally positively correlated with formation pressure. The accurate stratum pressure prediction result can provide important information for determining the density of the mud in the drilling process, and the proper mud density proportion can reduce the pollution of the mud to an undisturbed stratum and reduce the occurrence probability of accidents such as blowout and the like.

The most well-established formation pore pressure calculation theory today is the under-compaction theory proposed by Terzaghi. This theory holds that the formation Pore fluid Pressure (PP) is equal to the difference between the overburden formation Pressure (OBP) and the Vertical Effective Stress (VES). OBP may be calculated by integrating the density of the overburden. Therefore, the core of pore pressure calculation is how to obtain the interparticle vertical stress Values (VES). Accurate VES value determination is central to the calculation of PP.

The core of VES calculations requires the construction of a reasonable Normal Compaction Trend (NCT: Normal Compaction Trend). During the deposition process of the sand shale stratum, along with the gradual compaction of the sediment, stratum fluid in the shale pores is gradually discharged due to the deposition compaction effect, and accordingly a normal compaction trend line is displayed on a logging curve, namely a density curve is gradually and linearly increased, an acoustic curve is gradually reduced, and a resistivity curve is gradually increased due to the improvement of the mineralization degree. If the deposit is subjected to additional pressure during compaction causing formation fluids to not drain properly and is under-compacted, the log will correspondingly deviate from the normal trend line.

Based on the under-compaction theory, the current solution of the formation pore pressure mainly comprises an empirical coefficient method, an equivalent depth method, an Eaton method and a Bowers method.

The empirical coefficient method is suitable for the area which has measured data of a certain number of formation pore pressures. And establishing a sound wave time difference normal trend line equation by using data of drilling midway test, well completion oil test, RFT test and the like in the region, and then regressing an empirical coefficient formula to calculate the formation pore pressure. However, the method has the limitation that the stratum pressure in a work area must be reasonably known, and at the present stage, most of unconventional exploration areas have the problems of less data, low development degree and the like, so the method has strong limitation. The equivalent depth method is also called a balanced depth method, and is one of the most effective methods in the most basins in the world in the aspects of stratum pressure prediction and detection. From the principles of rock mechanics, it can be seen that the same value of porosity (or other physical parameter that reflects porosity) corresponds to the same effective stress, whether in the normal compacted zone or the under-compacted zone. The equilibrium depth method is believed to preserve the porosity value of the observation point in the underbalanced zone because the formation at that point is completely sealed at the equivalent depth of burial into the normal zone, with the subsequent application of increased overburden to the pore fluid. The Eaton method is a stratum pore pressure calculation method commonly adopted by oil field companies at home and abroad, and has the characteristics of high calculation precision, wide application range and the like. The Eaton method mainly utilizes the relation between seismic velocity and vertical effective stress, and the method mainly solves the formation pressure based on a velocity change trend line under normal bottom compaction conditions. The Bowers method is based on the determination of VES, and takes the unloading state caused by fluid expansion into consideration, and utilizes OBP to obtain PP, and practice proves that the method is more accurate in predicting high pressure generated by unbalanced compaction.

The above mentioned conventional formation pressure methods are all based on under-compaction theory, and the greatest disadvantage of under-compaction theory is that the NCT curve needs to be constructed artificially, and in order to avoid the artificial influence brought by the NCT curve, some scholars try to jump out of under-compaction theory to perform pressure prediction. The method does not need to construct NCT, and finally calculates the formation pressure by calculating the maximum compaction speed and the minimum compaction speed of the formation and further calculating the seismic interval velocity converted by a DIX formula. The method is developed to a certain extent subsequently, and is famous for a Liu Ji formula method (1993) proposed by Liu Ji and a Yunmei formula method (1996) proposed by Yunmei. In recent years, grand we (2015) proposed an API method for constructing a formation pressure prediction model suitable for a specific area by performing parameter screening using a correspondence relationship between formation pressure and other elastic parameters.

Most of the existing methods are based on the under-compaction theory, but the method has the defects that the prediction result of the method depends on the construction of a normal compaction trend line (NCT) to a great extent, and the construction of different NCT curves can directly influence the prediction result. The conventional NCT trend line construction method is mostly suitable for continuously sedimentary marine formations, and the NCT construction aiming at the land-phase intersalt formations needs to be further researched. While some scholars have attempted to jump out of the theory of under-compaction for pressure prediction, most methods have large area limitations if not entirely accounting for the effects of compaction, since compaction is one of the important causes of aberrant pressure development. Particularly, for a continental facies salt-rock stratum with a complex pressure cause, because the longitudinal change of lithology of the continental facies salt-rock stratum is abnormal and violent, the salt-rock stratum has a good blocking effect on abnormal pressure, and how to accurately predict the abnormal pressure of the salt-rock stratum faces more challenges. Therefore, it is necessary to develop a method, an apparatus, an electronic device and a medium for predicting the pressure of the salt formation.

The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

Disclosure of Invention

The invention provides a method, a device, electronic equipment and a medium for predicting the stratum pressure between salts, which can acquire elastic information under normal pressure conditions by constructing a rock physical model between salts, improve the precision of a compaction trend line, and effectively improve the stratum pressure prediction precision by combining an Eaton stratum pressure prediction method.

In a first aspect, an embodiment of the present disclosure provides a method for predicting a pressure of an intersalt formation, including:

constructing a rock physical model of the salt stratum;

calculating the elasticity tensor of the stratum between the salts according to the rock physical model;

calculating the normal compaction longitudinal wave speed of each depth according to the elasticity tensor;

and constructing a normal compaction trend line according to the normal compaction longitudinal wave speed of each depth, and calculating the formation pressure of the target depth.

Preferably, constructing the petrophysical model of the intersalt formation comprises: according to the VRH average theory, uniformly mixing salt rock, glauberite and quartz minerals to obtain a mixture between salts; according to the DEM theory, adding kerogen into the salt mixture to obtain an organic-rich salt mixture; calculating the wet porosity and further calculating the wet clay skeleton; according to the DEM theory, adding the wet clay skeleton into the organic-rich salt rock mixture to obtain a wet mineral skeleton; according to the Gassmann theory, dry pores are added into the wet mineral skeleton to obtain a rock physical model.

Preferably, the wet porosity is calculated by the formula (1):

wherein the content of the first and second substances,is the wet porosity of the clay, f_cIn order to consider the volume percentage of the clay in the pores,f_c ^mthe mineral body occupied by clay when the pores are not consideredThe percentage of the product is that the volume percentage,is the total porosity.

Preferably, the wet clay framework is calculated by formula (2):

wherein M is_wetIs the elasticity tensor of the wet clay skeleton, M_clayIs the elasticity tensor of clay.

Preferably, the petrophysical model is calculated by equation (3):

wherein the content of the first and second substances,for the elasticity parameter of the pore fluid, refer to Table 1, M_mix2Is the elastic tensor of the petrophysical model, M_mix1Is the elasticity tensor of the wet mineral skeleton.

Preferably, the normal compaction longitudinal wave velocity is calculated by equation (4):

wherein v is_{p_depth}For normal compaction longitudinal wave velocity, K and μ are the elastic tensors, and ρ is the total density for the corresponding depth.

Preferably, the formation pressure at the target depth is calculated by equation (5):

wherein, P_pPressure value to be determined, P, for a target depth_ovTo overburden pressure value，P_wAnd v is the measured speed value of the target depth.

As a specific implementation of the embodiments of the present disclosure,

in a second aspect, an embodiment of the present disclosure further provides an apparatus for predicting a pressure of an intersalt formation, including:

the construction module is used for constructing a rock physical model of the salt stratum;

the elastic tensor calculation module is used for calculating the elastic tensor of the stratum between the salts according to the rock physical model;

the longitudinal wave velocity calculation module is used for calculating the normal compaction longitudinal wave velocity of each depth according to the elasticity tensor;

and the formation pressure calculation module is used for constructing a normal compaction trend line according to the normal compaction longitudinal wave speed of each depth and calculating the formation pressure of the target depth.

Preferably, constructing the petrophysical model of the intersalt formation comprises: according to the VRH average theory, uniformly mixing salt rock, glauberite and quartz minerals to obtain a mixture between salts; according to the DEM theory, adding kerogen into the salt mixture to obtain an organic-rich salt mixture; calculating the wet porosity and further calculating the wet clay skeleton; according to the DEM theory, adding the wet clay skeleton into the organic-rich salt rock mixture to obtain a wet mineral skeleton; according to the Gassmann theory, dry pores are added into the wet mineral skeleton to obtain a rock physical model.

Preferably, the wet porosity is calculated by the formula (1):

wherein the content of the first and second substances,is the wet porosity of the clay, f_cIn order to consider the volume percentage of the clay in the pores,f_c ^min order to take the volume percentage of the mineral occupied by the clay regardless of the porosity,is the total porosity.

Preferably, the wet clay framework is calculated by formula (2):

wherein M is_wetIs the elasticity tensor of the wet clay skeleton, M_clayIs the elasticity tensor of clay.

Preferably, the petrophysical model is calculated by equation (3):

wherein the content of the first and second substances,for the elasticity parameter of the pore fluid, refer to Table 1, M_mix2Is the elastic tensor of the petrophysical model, M_mix1Is the elasticity tensor of the wet mineral skeleton.

Preferably, the normal compaction longitudinal wave velocity is calculated by equation (4):

wherein v is_{p_depth}For normal compaction longitudinal wave velocity, K and μ are the elastic tensors, and ρ is the total density for the corresponding depth.

Preferably, the formation pressure at the target depth is calculated by equation (5):

wherein，P_pPressure value to be determined, P, for a target depth_ovTo overburden pressure value, P_wAnd v is the measured speed value of the target depth.

In a third aspect, an embodiment of the present disclosure further provides an electronic device, where the electronic device includes:

a memory storing executable instructions;

a processor executing the executable instructions in the memory to implement the method for intersalt formation pressure prediction.

In a fourth aspect, the disclosed embodiments also provide a computer-readable storage medium, which stores a computer program, and when the computer program is executed by a processor, the computer program implements the method for predicting the pressure of the salt formation.

The beneficial effects are that:

(1) the construction of the compaction trend line is the core of the pressure prediction. Because the longitudinal change of the lithology of the stratum between the salts is severe, the pressure prediction method based on the rock physical modeling considers the influence of the lithology speed, can better depict the trend of the speed changing along with the lithology, obtains a more accurate compaction trend line, and lays a foundation for the subsequent pressure prediction.

(2) The change of the velocity values of different depths in the underground can be caused by different pressures and violent change of lithology, so that the multi-solution exists, and the multi-solution is particularly suitable for the characteristics of the stratum between the salts. The method can enable the compaction trend line to eliminate the interference of lithology on the compaction trend line, so that the pressure prediction is more accurate.

(3) The pressure prediction process based on the rock physics is characterized in that all input parameters are based on logging data and driven by the data, so that the interference of human factors caused by manually determining a compaction trend line by a conventional method is avoided.

(4) The salt rock physical model constructed aiming at the salt stratum can better reflect the elastic information of the salt stratum under the normal pressure condition.

The method and apparatus of the present invention have other features and advantages which will be apparent from or are set forth in detail in the accompanying drawings and the following detailed description, which are incorporated herein, and which together serve to explain certain principles of the invention.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings, in which like reference numerals generally represent like parts.

Fig. 1 shows a schematic representation of under-compaction theory.

FIG. 2 shows a flow diagram for the salt formation petrophysical modeling according to an embodiment of the present invention.

FIG. 3 shows a flow chart of steps of a method of salt formation pressure prediction according to an embodiment of the invention.

FIG. 4 shows a schematic view of a typical formation of a salt formation according to one embodiment of the invention.

Fig. 5 a-5 d show schematic diagrams of well logs according to an embodiment of the present invention.

FIG. 6 illustrates a schematic of normal compaction trend lines for longitudinal wave velocity according to an embodiment of the present disclosure.

FIG. 7 shows a schematic diagram of pressure prediction results according to an embodiment of the invention.

FIG. 8 shows a block diagram of an intersalt formation pressure prediction apparatus according to an embodiment of the invention.

Description of reference numerals:

201. building a module; 202. an elasticity tensor calculation module; 203. a longitudinal wave velocity calculation module; 204. and a formation pressure calculation module.

Detailed Description

Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein.

Fig. 1 shows a schematic representation of under-compaction theory. The theory holds that overburden formation pressure is equal to the sum of formation pore fluid pressure and vertical effective stress. The physical meaning of the method can be expressed as that the pressure value of the fluid in the pore space is equal to the sum of the pressures of the overlying strata minus the vertical stress among the framework particles. The OBP is relatively well calculated, and the OBP can be calculated by integrating the density of the overburden through a density logging curve. Therefore, the core of pore pressure calculation is how to obtain the interparticle vertical stress Values (VES). Accurate VES value determination is central to the calculation of PP. The VES may be calculated using the difference between the velocity of the formation at atmospheric pressure and the velocity at the anomalous pressure. The formation speed under abnormal pressure, namely the speed obtained by underground actual measurement, can be obtained through acoustic time difference logging, and the formation speed under normal pressure needs to be obtained based on an NCT curve. To summarize, the key to formation pressure calculation is how VES values are obtained, while the key to VES value calculation is the determination of the NCT curve.

FIG. 2 shows a flow diagram for the salt formation petrophysical modeling according to an embodiment of the present invention.

The invention provides a method for predicting the pressure of a formation between salts, which comprises the following steps:

constructing a rock physical model of the salt stratum; in one example, constructing a petrophysical model of an intersalt formation includes: according to the VRH average theory, uniformly mixing salt rock, glauberite and quartz minerals to obtain a mixture between salts; according to the DEM theory, adding kerogen into the salt mixture to obtain an organic substance-rich salt mixture; adding clay into the wet pores to obtain wet clay; according to the DEM theory, adding wet clay into the organic-rich salt rock mixture to obtain a wet mineral framework; according to the Gassmann theory, dry porosity was added to the wet mineral skeleton to obtain a petrophysical model, as shown in FIG. 2.

The average theoretical formula of VRH is:

wherein i represents the i-th mineral, f_iAs a percentage of the volume content of the mineral, the percentage of each mineral by volume varies with depth, M_VRHAs a mixture between salts, M_iThe specific values of the elastic modulus of the ith mineral, including the bulk modulus and the shear modulus, are shown in table 1, and the elastic modulus of the minerals in different regions may be slightly different, particularly based on local laboratory test samples.

TABLE 1

The DEM theory is formula (9), kerogen is added into the mixture between the salts through formula (9), and finally the elasticity tensor of the mixture rich in organic rock salt is obtained:

wherein, K₁，μ₁Is the bulk modulus and shear modulus of the salt mixture, K₂，μ₂Is the bulk and shear modulus of kerogen, K_mix1，μ_mix1Is the bulk and shear modulus of the salt-salt mixture, y is the volume percentage of kerogen as a function of depth, and P and Q are shape factors that control the shape of the package.

The wet porosity was calculated by equation (1):

wherein the content of the first and second substances,is the wet porosity of the clay, f_cIn order to consider the volume percentage of the clay in the pores,f_c ^min order to take the volume percentage of the mineral occupied by the clay regardless of the porosity,the total porosity can be directly obtained by logging.

Then the wet clay framework is calculated by equation (2):

wherein M is_wetIs the elasticity tensor of the wet clay skeleton, M_clayIs the elasticity tensor of clay.

And (3) adding the wet clay framework into the organic-rich rock salt mixture by utilizing the DEM theory to obtain the wet mineral framework.

Dry porosity was calculated by equation (10):

adding dry pores into a wet mineral skeleton by using a formula (3) to obtain a rock physical model:

wherein the content of the first and second substances,for the elasticity parameter of the pore fluid, refer to Table 1, M_mix2Is the elastic tensor of the petrophysical model, M_mix1Is the elasticity tensor of the wet mineral skeleton.

The mineral composition, porosity and density logs at each depth are input to a petrophysical model, and the elasticity tensor of the deep intersalt formation is calculated.

Calculating the normal compaction longitudinal wave speed of each depth according to the elasticity tensor of the stratum between the salts; in one example, normal compaction compressional velocity is calculated by equation (4):

wherein v is_{p_depth}For normal compaction longitudinal wave velocity, K and μ are the elastic tensors, and ρ is the total density for the corresponding depth.

According to the normal compaction longitudinal wave speed of each depth, a normal compaction trend line related to the longitudinal wave speed is constructed, and the formation pressure of the target depth is calculated; in one example, the formation pressure at the target depth is calculated by equation (5):

wherein, P_pPressure value to be determined, P, for a target depth_ovTo overburden pressure value, P_wAnd v is the measured speed value of the target depth.

The normal compaction trend line (NCT) of the prior art, which is generally a velocity curve that increases slowly with depth, is substituted into equation (5) to calculate the pressure value for the conventional method. However, the method neglects the influence of lithology change on NCT trend, the method substitutes the influence of lithology change of different depths into pressure prediction, so that a newly constructed normal compaction trend line is not an approximate straight line any more, but a curve which continuously changes along with the depth, and the speed on the trend line of the method is substituted into a formula (5), and the formation pressure value of the target depth can be calculated.

The invention also provides a device for predicting the formation pressure between the salts, which comprises:

the construction module is used for constructing a rock physical model of the salt stratum; in one example, constructing a petrophysical model of an intersalt formation includes: according to the VRH average theory, uniformly mixing salt rock, glauberite and quartz minerals to obtain a mixture between salts; according to the DEM theory, adding kerogen into the salt mixture to obtain an organic substance-rich salt mixture; adding clay into the wet pores to obtain wet clay; according to the DEM theory, adding wet clay into the organic-rich salt rock mixture to obtain a wet mineral framework; according to the Gassmann theory, dry pores are added into a wet mineral skeleton to obtain a rock physical model.

The average theoretical formula of VRH is:

wherein i represents the i-th mineral, f_iAs a percentage of the volume content of the mineral, the percentage of each mineral by volume varies with depth, M_VRHAs a mixture between salts, M_iThe specific values of the elastic modulus of the ith mineral, including the bulk modulus and the shear modulus, are shown in table 1, and the elastic modulus of the minerals in different regions may be slightly different, particularly based on local laboratory test samples.

The DEM theory is formula (9), kerogen is added into the mixture between the salts through formula (9), and finally the elasticity tensor of the mixture rich in organic rock salt is obtained:

wherein, K₁，μ₁Is the bulk modulus and shear modulus of the salt mixture, K₂，μ₂Is the bulk and shear modulus of kerogen, K_mix1，μ_mix1Is the bulk and shear modulus of the salt-salt mixture, y is the volume percentage of kerogen as a function of depth, and P and Q are shape factors that control the shape of the package.

The wet porosity was calculated by equation (1):

wherein the content of the first and second substances,is the wet porosity of the clay, f_cIn order to consider the volume percentage of the clay in the pores,f_c ^min order to take the volume percentage of the mineral occupied by the clay regardless of the porosity,the total porosity can be directly obtained by logging.

Then the wet clay framework is calculated by equation (2):

wherein M is_wetIs the elasticity tensor of the wet clay skeleton, M_clayIs the elasticity tensor of clay.

And (3) adding the wet clay framework into the organic-rich rock salt mixture by utilizing the DEM theory to obtain the wet mineral framework.

Dry porosity was calculated by equation (10):

adding dry pores into a wet mineral skeleton by using a formula (3) to obtain a rock physical model:

wherein the content of the first and second substances,for the elasticity parameter of the pore fluid, refer to Table 1, M_mix2Is the elastic tensor of the petrophysical model, M_mix1Is the elasticity tensor of the wet mineral skeleton.

And the elastic tensor calculation module is used for inputting the mineral composition, porosity and density logging curves of all depths into the rock physical model and calculating the elastic tensor of the stratum between the depth and the salt.

The longitudinal wave velocity calculation module is used for calculating the normal compaction longitudinal wave velocity of each depth according to the elasticity tensor of the stratum between the salts; in one example, normal compaction compressional velocity is calculated by equation (4):

wherein v is_{p_depth}For normal compaction longitudinal wave velocity, K and μ are the elastic tensors, and ρ is the total density for the corresponding depth.

The formation pressure calculation module is used for constructing a normal compaction trend line related to the longitudinal wave speed according to the normal compaction longitudinal wave speed of each depth and calculating the formation pressure of the target depth; in one example, the formation pressure at the target depth is calculated by equation (5):

wherein, P_pPressure value to be determined, P, for a target depth_ovTo overburden pressure value, P_wAnd v is the measured speed value of the target depth.

The present invention also provides an electronic device, comprising: a memory storing executable instructions; and a processor executing executable instructions in the memory to implement the method for predicting the pressure of the salt formation.

The present invention also provides a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, implements the method of inter-salt formation pressure prediction described above.

To facilitate understanding of the scheme of the embodiments of the present invention and the effects thereof, four specific application examples are given below. It will be understood by those skilled in the art that this example is merely for the purpose of facilitating an understanding of the present invention and that any specific details thereof are not intended to limit the invention in any way.

Example 1

FIG. 3 shows a flow chart of steps of a method of salt formation pressure prediction according to an embodiment of the invention.

As shown in fig. 3, the method for predicting the pressure of the salt formation includes: step 101, constructing a rock physical model of a salt stratum; 102, calculating the elasticity tensor of the stratum between the salts according to the rock physical model; step 103, calculating the normal compaction longitudinal wave speed of each depth according to the elasticity tensor; and 104, constructing a normal compaction trend line according to the normal compaction longitudinal wave speed of each depth, and calculating the formation pressure of the target depth.

Fig. 4 is a schematic diagram of a typical formation of a salt-rock formation according to an embodiment of the present invention, which is composed of two sets of salt rocks, one set of salt-rock formation, the thickness of the salt rocks is usually about 10-25 m, the salt-rock formation has low porosity and poor permeability, and can perform a better pressure plugging function. The thickness of the salt-space stratum is usually between 5 and 38 meters, and the porosity of the salt-space stratum is relatively high due to the thermal evolution of organic matters and the like, so that the salt-space stratum is an unconventional reservoir which is self-generated and self-stored.

Fig. 5 a-5 d show schematic diagrams of well logs according to an embodiment of the present invention. The gamma, the longitudinal wave velocity, the density and the porosity are sequentially arranged from left to right. Logging of salt formations correspondingly manifests as low GR, high velocity, low density, low porosity, while intersalt formations manifest as high GR, low velocity, medium density, high porosity.

FIG. 6 illustrates a schematic of normal compaction trend lines for longitudinal wave velocity according to an embodiment of the present disclosure. As can be seen, the dotted line is the NCT line constructed by the conventional method, the gray solid line is the NCT line calculated by the method, and the black solid line is the measured longitudinal wave velocity. The characteristics of the three curves are obvious, and the dotted line reflects the trend of the speed changing along with the depth and is generally expressed as a straight line; and the gray solid line and the actually measured black solid line show a severe change trend, and the depth section is a saline interprosodic layer with severe lithological change as can be known by comparing with a geological stratification result. Thus, the periodic jitter of the measured curve is largely caused by the drastic changes in the lithology longitudinal direction. Velocity is a parameter influenced by both pore pressure and lithology, and a salt prosody layer with violent lithology change cannot be described by using a single NCT line, and only the influence of pore pressure on velocity is considered, and the influence of lithology is ignored. Finally, the pore pressure prediction result contains lithology information, so that the final pressure prediction result is high and low. However, the gray NCT line constructed by the salt rock physical model of the method changes along with the change of the lithology, and the result contains the change information of the longitudinal lithology, so that the prediction result of the pore pressure is more accurate.

FIG. 7 shows a schematic diagram of pressure prediction results according to an embodiment of the invention. The hollow point is the mud density, the gray curve is the conventional pore pressure prediction result, and the black thick solid line is the prediction result of the new method. By comparison, the conventional predictions shown in grey are subject to strong longitudinal variations in salt-to-salt lithology, and the pore pressure predictions exhibit periodic jitter and exceed the mud density over many depth ranges. The mud density profile reflects the upper limit of formation pressure. When the pore pressure is higher than the mud density, accidents such as well kick and blowout occur, so in pressure prediction, the prediction result is usually measured by using the pore pressure. The influence of lithology on the pressure result prediction is eliminated based on the prediction result of the method, the pressure prediction value is mostly lower than the mud density value, and compared with the conventional method, the prediction result is more accurate and reasonable.

Example 2

FIG. 8 shows a block diagram of an intersalt formation pressure prediction apparatus according to an embodiment of the invention.

As shown in fig. 8, the device for predicting the pressure of the salt formation includes:

a construction module 201 for constructing a petrophysical model of the salt formation;

an elasticity tensor calculation module 202, which calculates the elasticity tensor of the interbalted stratum according to the rock physical model;

the longitudinal wave velocity calculation module 203 is used for calculating the normal compaction longitudinal wave velocity of each depth according to the elasticity tensor;

and the formation pressure calculation module 204 is used for constructing a normal compaction trend line according to the normal compaction longitudinal wave speed of each depth and calculating the formation pressure of the target depth.

Alternatively, constructing a petrophysical model of the intersalt formation comprises: according to the VRH average theory, uniformly mixing salt rock, glauberite and quartz minerals to obtain a mixture between salts; according to the DEM theory, adding kerogen into the salt mixture to obtain an organic substance-rich salt mixture; calculating the wet porosity and further calculating the wet clay skeleton; according to the DEM theory, adding a wet clay framework into the organic-rich salt rock mixture to obtain a wet mineral framework; according to the Gassmann theory, dry pores are added into a wet mineral skeleton to obtain a rock physical model.

Alternatively, the wet porosity is calculated by equation (1):

wherein the content of the first and second substances,is the wet porosity of the clay, f_cIn order to consider the volume percentage of the clay in the pores,f_c ^min order to take the volume percentage of the mineral occupied by the clay regardless of the porosity,is the total porosity.

As an alternative, the wet clay framework is calculated by equation (2):

wherein M is_wetIs the elasticity tensor of the wet clay skeleton, M_clayIs the elasticity tensor of clay.

Alternatively, the petrophysical model is calculated by equation (3):

wherein the content of the first and second substances,for the elasticity parameter of the pore fluid, refer to Table 1, M_mix2Is the elastic tensor of the petrophysical model, M_mix1Is the elasticity tensor of the wet mineral skeleton.

Alternatively, the normal compaction compressional velocity is calculated by equation (4):

wherein v is_{p_depth}For normal compaction longitudinal wave velocity, K and μ are the elastic tensors, and ρ is the total density for the corresponding depth.

Alternatively, the formation pressure at the target depth is calculated by equation (5):

wherein, P_pPressure value to be determined, P, for a target depth_ovTo overburden pressure value, P_wAnd v is the measured speed value of the target depth.

Example 3

The present disclosure provides an electronic device including: a memory storing executable instructions; and the processor executes the executable instructions in the memory to realize the method for predicting the pressure of the intersalt formation.

An electronic device according to an embodiment of the present disclosure includes a memory and a processor.

The memory is to store non-transitory computer readable instructions. In particular, the memory may include one or more computer program products that may include various forms of computer-readable storage media, such as volatile memory and/or non-volatile memory. The volatile memory may include, for example, Random Access Memory (RAM), cache memory (cache), and/or the like. The non-volatile memory may include, for example, Read Only Memory (ROM), hard disk, flash memory, etc.

The processor may be a Central Processing Unit (CPU) or other form of processing unit having data processing capabilities and/or instruction execution capabilities, and may control other components in the electronic device to perform desired functions. In one embodiment of the disclosure, the processor is configured to execute the computer readable instructions stored in the memory.

Those skilled in the art should understand that, in order to solve the technical problem of how to obtain a good user experience, the present embodiment may also include well-known structures such as a communication bus, an interface, and the like, and these well-known structures should also be included in the protection scope of the present disclosure.

For the detailed description of the present embodiment, reference may be made to the corresponding descriptions in the foregoing embodiments, which are not repeated herein.

Example 4

Embodiments of the present disclosure provide a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, implements the method for predicting a formation pressure between salts.

A computer-readable storage medium according to an embodiment of the present disclosure has non-transitory computer-readable instructions stored thereon. The non-transitory computer readable instructions, when executed by a processor, perform all or a portion of the steps of the methods of the embodiments of the disclosure previously described.

The computer-readable storage media include, but are not limited to: optical storage media (e.g., CD-ROMs and DVDs), magneto-optical storage media (e.g., MOs), magnetic storage media (e.g., magnetic tapes or removable disks), media with built-in rewritable non-volatile memory (e.g., memory cards), and media with built-in ROMs (e.g., ROM cartridges).

It will be appreciated by persons skilled in the art that the above description of embodiments of the invention is intended only to illustrate the benefits of embodiments of the invention and is not intended to limit embodiments of the invention to any examples given.

Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.